Microwave probe, plasma monitoring system including the microwave probe, and method for fabricating semiconductor device using the system

ABSTRACT

Disclosed herein are a microwave probe capable of precisely detecting a plasma state in a plasma process, a plasma monitoring system including the probe, and a method of fabricating a semiconductor device using the system. The microwave probe includes a body extending in one direction and a head which is connected to one end of the body and has a flat plate shape. In addition, in the plasma process, the microwave probe is non-invasively coupled to a chamber such that a surface of the head contacts an outer surface of a viewport of the chamber, and the microwave probe applies a microwave into the chamber through the head and receives signals generated inside the chamber through the head.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No.10-2015-0124942, filed on Sep. 3, 2015, the disclosure of which isincorporated by reference herein in its entirety.

BACKGROUND

The inventive concept relates to an apparatus and a method forfabricating a semiconductor device, and more particularly, to anapparatus for monitoring a plasma state in a plasma process, and amethod for fabricating a semiconductor device using the apparatus.

Plasma is being widely used for processes of manufacturingsemiconductors, plasma display panels (PDPs), liquid crystal displays(LCDs), solar cells, and the like. Representative plasma processesinclude dry etching, plasma enhanced chemical vapor deposition (PECVD),sputtering, ashing, and the like. Generally, capacitively coupled plasma(CCP), inductively coupled plasma (ICP), helicon plasma, microwaveplasma, and the like are being used. It is known that plasma processesare directly associated with plasma parameters (for example, an electrondensity, an electron temperature, an ion flux, and ion energy), andthat, in particular, an electron density is closely related tothroughput. Therefore, a plasma source having a high electron density isbeing actively developed.

SUMMARY

The inventive concept provides a microwave probe capable of preciselydetecting a plasma state in a plasma process, a plasma monitoring systemincluding the probe, and a method of fabricating a semiconductor deviceusing the system.

According to an aspect of the inventive concept, there is provided amethod of fabricating a semiconductor device, which includes:non-invasively coupling a microwave probe to a viewport of a chamber fora plasma process; arranging a wafer inside the chamber; generatingplasma by injecting a process gas into the chamber and applying RF powerto the chamber; applying a microwave into the chamber through themicrowave probe, and receiving signals generated inside the chamberthrough the microwave probe; and detecting a resonant frequency amongthe received signals, and analyzing a plasma state inside the chamberbased on the resonant frequency, wherein the microwave probe includes abody and a head at one end of the body, and applies the microwave andreceives the signals through the head contacting an outer surface of theviewport.

According to another aspect of the inventive concept, there is provideda method of fabricating a semiconductor device, which includes:generating plasma by injecting a process gas into a chamber in which awafer is arranged and by applying RF power to the chamber; applying amicrowave into the chamber and receiving signals generated inside thechamber, through a microwave probe non-invasively coupled to a viewportof the chamber, the microwave probe including a body and a head at oneend of the body; and detecting a resonant frequency among the receivedsignals, and analyzing a plasma state inside the chamber based on theresonant frequency.

According to a further aspect of the inventive concept, there isprovided a microwave probe which includes: a body extending in onedirection; and a head which is connected to one end of the body and hasa flat plate structure, wherein in a plasma process, the microwave probeis configured to be non-invasively coupled to a chamber such that asurface of the head contacts an outer surface of a viewport of thechamber, and configured to apply a microwave into the chamber and toreceive signals generated inside the chamber through the head.

According to yet another aspect of the inventive concept, there isprovided a plasma monitoring system which includes: a chamber for aplasma process; an RF power supply for generating plasma inside thechamber; a microwave probe configured to be non-invasively coupled to aviewport included in the chamber, the microwave probe including a bodyand a head at one end of the body; and a network analyzer configured tobe electrically connected to the microwave probe.

According to yet another aspect of the inventive concept, there isprovided a method of fabricating a semiconductor device. The methodincludes: non-invasively coupling a microwave probe to a viewport heldin an outer wall of a chamber for a plasma process; generating plasma byinjecting a process gas into the chamber and applying RF power to thechamber; applying a microwave into the chamber through the microwaveprobe; receiving signals generated inside the chamber through themicrowave probe; detecting a resonant frequency among the receivedsignals; and analyzing a plasma state inside the chamber based on theresonant frequency including determining an electron density of theplasma based on the resonant frequency. The microwave probe includes abody and a head at a first end of the body, and the applying of themicrowave and the receiving of the signals are performed through thehead which contacts an outer surface of the viewport during thenon-invasively coupling the microwave probe to the viewport.

According to the inventive concept, in a plasma process, the microwaveprobe is non-invasively coupled to the viewport of the chamber, and thuscan be advantageously used for monitoring a plasma state inside thechamber. For example, since the microwave probe is non-invasivelycoupled to an outside of the chamber, the microwave probe itself doesnot affect a plasma state inside the chamber. In addition, using thenon-invasive microwave probe, a microwave is applied, and signals insidethe chamber are received, whereby the plasma state inside the chambercan be accurately detected and monitored.

According to the inventive concept, the plasma monitoring systemincludes the microwave probe non-invasively coupled to the viewport ofthe chamber, whereby the plasma state inside the chamber can beaccurately detected without an influence on the plasma state inside thechamber. In addition, the plasma monitoring system precisely monitorswhether there is a problem in the plasma state by calculating anelectron density based on the measured resonant frequency, and controlsprocess conditions of a plasma process, thereby optimizing the plasmaprocess.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments of the inventive concept will be more clearlyunderstood from the following detailed description taken in conjunctionwith the accompanying drawings in which:

FIGS. 1A and 1B are a perspective view and a side view of a microwaveprobe according to an example embodiment of the inventive concept;

FIGS. 2A to 2D are a perspective view, plan views, and a sectional viewof a microwave probe according to an example embodiment of the inventiveconcept;

FIGS. 3A and 3B are a plan view and a sectional view of a microwaveprobe according to an example embodiment of the inventive concept;

FIGS. 4A and 4B are a perspective view and a plan view of a microwaveprobe according to an example embodiment of the inventive concept;

FIG. 5 illustrates plan views of various shapes of head surfaces ofmicrowave probes according to example embodiments of the inventiveconcept;

FIG. 6 illustrates perspective views of various shapes of bodies ofmicrowave probes according to example embodiments of the inventiveconcept;

FIGS. 7A and 7B are sectional views of microwave probes according toexample embodiments of the inventive concept;

FIGS. 8A and 8B are a sectional view and a plan view of the microwaveprobe of FIG. 2A, which is coupled to a chamber;

FIGS. 9A and 9B are a sectional view and a plan view of the microwaveprobe of FIG. 3A, which is coupled to a chamber;

FIG. 10 is a plan view of the microwave probe of FIG. 2A, which iscoupled to a chamber;

FIG. 11 is a conceptual diagram for explaining a method of detecting aplasma state inside a chamber using a microwave probe according to anexample embodiment of the inventive concept;

FIGS. 12A and 12B are sectional views of microwave probes according toexample embodiments of the inventive concept, which are coupled todifferently-shaped viewports included in chambers;

FIGS. 13A and 13B are graphs depicting reflection coefficients alongwith frequencies while a pressure and applied power inside a chamber arechanged, using a microwave probe according to an example embodiment ofthe inventive concept;

FIG. 14 is a graph depicting a correlation between an oscillationfrequency of plasma and an absorption frequency of a surface wavedepending upon a pressure change;

FIG. 15 is a schematic configuration diagram of a plasma monitoringsystem including a microwave probe according to an example embodiment ofthe inventive concept;

FIG. 16 is a graph showing a concept for determining a time point ofstabilization of plasma inside a chamber using a plasma monitoringsystem according to an example embodiment of the inventive concept;

FIG. 17 is a conceptual diagram for explaining utilization of a plasmamonitoring system according to an example embodiment of the inventiveconcept relating to tool matching between chambers;

FIG. 18 is a graph showing a concept for determining a time point ofpreventive maintenance (PM) of a chamber using a plasma monitoringsystem according to an example embodiment of the inventive concept;

FIG. 19 is a graph depicting electron densities of plasma detected usinga plasma monitoring system according to an example embodiment of theinventive concept in plasma processes for a first wafer and a ninthwafer;

FIG. 20 is a flow chart illustrating a process of monitoring a plasmastate and controlling a plasma process according to an exampleembodiment of the inventive concept; and

FIG. 21 is a flow chart illustrating a process of fabricating asemiconductor device through control of a plasma process according to anexample embodiment of the inventive concept.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, example embodiments of the inventive concept will bedescribed in detail with reference to the accompanying drawings. Itshould be understood that the example embodiments are provided forcomplete disclosure and thorough understanding of the inventive conceptby those of ordinary skill in the art, and that the inventive concept isnot limited to the following embodiments and may be embodied indifferent ways.

As used herein, the term “and/or” includes any and all combinations ofone or more of the associated listed items. Expressions such as “atleast one of,” when preceding a list of elements, modify the entire listof elements and do not modify the individual elements of the list.

It will be understood that when a component is referred to as beingconnected to another component, the component may be directly connectedto the other component, or a third component may also be interposedtherebetween. Similarly, when a component is referred to as being placedon another component, the component may be directly placed on the othercomponent, or a third component may also be interposed therebetween. Inthe drawings, the sizes or structures of components may be exaggeratedfor clarity, and portions not essential to the description may beomitted for clarity. Like components will be denoted by like referencenumerals throughout the specification. In addition, the terminology usedherein is only for the purpose of describing specific embodiments of theinventive concept and is not intended to limit the inventive concept.

FIGS. 1A and 1B are a perspective view and a side view of a microwaveprobe according to an example embodiment of the inventive concept.

Referring to FIGS. 1A and 1B, a microwave probe 100 according to thepresent example embodiment may include a body 110, a head 120, and aconnector 130.

The body 110 may include a metal layer 112 and an insulation coveringlayer 114 surrounding the metal layer 112. The metal layer 112 mayinclude, for example, a metal having good electrical conductivity, suchas copper (Cu), aluminum (Al), and the like. The metal layer 112 may beflexible. However, in some cases, flexibility of the metal layer 112 maybe suppressed due to an increase in hardness or thickness of the metallayer 112. The metal layer 112 may have a pillar or line shape extendingin one direction. The metal layer 112 may have a thickness of about 1 mmand a length of a few centimeters. Of course, the thickness and lengthof the metal layer 112 are not limited thereto. For reference, thethickness of the metal layer 112 may refer to a diameter when the metallayer 112 has a circular pillar shape, and may refer to a length of athinner side when the metal layer 112 has a rectangular or quadrangularpillar shape. In some embodiments, the metal layer 112 is a rod.

The insulation covering layer 114 may serve to protect the metal layer112 and to insulate the metal layer 112 from other conductive materialsexternal to the metal layer 112. For example, as shown in FIGS. 2A to2D, when a microwave probe 100 a includes a conductive ground cover 140,the insulation covering layer 114 may serve to insulate the metal layer112 and the ground cover 140 from each other. The insulation coveringlayer 114 may include, for example, cotton, natural rubber, syntheticrubber, a synthetic resin (or plastic), ceramic, or the like.

The insulation covering layer 114 may have a cylindrical tube shapesurrounding the metal layer 112. Of course, the shape of the insulationcovering layer 114 is not limited thereto. The body 110 including theinsulation covering layer 114 may have a first thickness T1 of, forexample, 10 mm or less. However, the thickness of the body 110 is notlimited thereto. The insulation covering layer 114 may be flexible inconjunction with the metal layer 112. Thus, the body 110 as a whole maybe flexible. When flexibility of the metal layer 112 is suppressed,flexibility of the insulation covering layer 114 may also be suppressed,and thus, the insulation covering layer 114 may include a high-hardnessplastic or ceramic.

The body 110 may be formed in the same or similar structure as cablesused for RF signal transfer. For example, the body 110 may includevarious RF cables such as RG 58, RG 316, RG 400, RG 402, RG 405, SF/SR085, SF/SR 141, LMR 200 cables, and the like. In some cases, theinsulation covering layer 114 may not be formed in or on the body 110.In other words, the body 110 may include only the metal layer 112, andan outer surface of the metal layer 112 may be exposed to the outside ofthe metal layer 112. Specific shapes of the body 110 will be describedbelow in more detail with reference to FIG. 6.

The head 120 may be coupled to one end of the body 110, and may have aflat plate structure. For example, the head 120 may have a circular flatplate structure such as a disk. Of course, the structure of the head 120is not limited thereto. The head 120 may include a metal having goodconductivity, such as Cu, Al, and the like, similar to the metal layer112. For example, the head 120 of the microwave probe 100 may includeCu.

The head 120 may have a different area according to sizes of a viewport(see the reference numeral 220 in FIGS. 8A and 8B) mounted on a chamber.For example, when the head 120 is formed in a circular flat platestructure, the head 120 may have a first diameter D1 of 75% or 80% ormore of a diameter of the viewport. For example, when the viewport has adiameter of 5 cm, the head 120 may have a first diameter D1 of 4 cm ormore. Of course, the area or diameter of the head 120 is not limited tothe numerical values set forth above. For example, the head 120 may havean area that is less than an area corresponding to 75% of the diameterof the viewport, or in some cases, may have an area that is greater thanthe area of the viewport. In addition, the head 120 may have a secondthickness T2 of 10 mm or less. However, the thickness of the head 120 isnot limited thereto.

The head 120 may be electrically connected to the metal layer of thebody 110. The head 120 may apply a microwave, which is transferred fromthe outside of the microwave probe 100 through the metal layer 112, intothe chamber (see the reference numeral 200 in FIG. 11 or 15). Inaddition, the head 120 may receive signals generated inside the chamberand transfer the signals to the outside of the microwave probe 100through the metal layer 112.

To improve the functionality of the head 120 for applying a microwaveand/or receiving signals, the head 120 may contact the viewport of thechamber. For example, when the microwave probe 100 is coupled to theviewport of the chamber in a plasma process, the microwave probe 100 maybe coupled to the viewport such that a surface of the head 120 contactsan outer surface of the viewport. In addition, to improve thefunctionality set forth above, various patterns may be formed on thesurface of the head 120 contacting the viewport. The structure of thehead 120, and the patterns formed on the surface of the head 120 will beexplained below in more detail in descriptions related to FIG. 5.

The connector 130 may be coupled to the other, opposite end of the body110. The connector 130 may be a connection device for electricallyconnecting an external cable or wire (see the reference numeral 310 inFIG. 8A) outside the microwave probe 100 to the body 110. The connector130 may be an RF connector transferring an RF signal such as microwavesand the like. For example, the connector 130 may include SubMiniature A(SMA), SubMiniature B (SMB), N type, Bayonet Neil-Concelman (BNC), TNC,7/16 DIN connectors, and the like. Of course, the connector 130 is notlimited to the connectors set forth above. The external wire connectedto the connector 130 may be an RF cable, for example, an RG 58, RG 316,RG 400, RG 402, RG 405, SF/SR 085, SF/SR 141, LMR 200 cable, or thelike. Of course, the external wire is not limited to the RF cables setforth above.

The connector 130 may be omitted from the microwave probe 100 accordingto the present example embodiment. For example, the body 110 of themicrowave probe 100 may be directly connected to a network analyzer (seethe reference numeral 300 in FIG. 15). That is, the body 110 may bedirectly connected to a connector mounted on the network analyzer. Here,the body 110 may be formed, for example, in an RF cable structure. Thenetwork analyzer may generate a microwave to transfer the microwave tothe outside thereof, and may receive a signal transferred from theoutside thereof to detect a resonant frequency or the like.

The microwave probe 100 according to the present example embodiment maybe non-invasively coupled to a viewport (see the reference numeral 220in FIG. 15) of a chamber (see the reference numeral 200 in FIG. 15) in aplasma process. Here, the term “non-invasively” may mean that themicrowave probe 100 is coupled to an outside of the chamber instead ofinvading or being inserted into the chamber. In addition, since themicrowave probe 100 does not invade into the chamber and thus does notcontact plasma, the non-invasive manner may also be referred to as anon-contact manner.

The microwave probe 100 may include a structure for coupling to thechamber. For example, the structure for coupling to the chamber may beformed on any one of the body 110, the head 120, and the connector 130.For example, a structure for various mechanical coupling, such as screwcoupling, hook coupling, wedge coupling, snap coupling, and the like,may be mounted on the microwave probe 100, and a structure correspondingto the above structure may be mounted on a wall of the chamber, wherebythe microwave probe 100 may be coupled to a viewport of the chamberusing the coupling features or manners set forth above. A structure suchas a vacuum sucker may be mounted on the microwave probe 100, wherebythe microwave probe 100 may be coupled to the viewport of the chamberthrough a vacuum suction principle. In addition, the microwave probe 100may also be coupled to the viewport of the chamber using an adhesivetape arranged on a surface of the head 120.

In some cases, the microwave probe 100 may be naturally coupled to theviewport of the chamber without a separate coupling means. For example,if the viewport is formed in a circular recessed structure, the head 120may be formed to a similar size to or substantially the same size as theviewport and inserted into the viewport having the recessed structure,whereby the microwave probe 100 can be naturally coupled to the viewportof the chamber.

The microwave probe 100 according to the present example embodiment maybe non-invasively coupled to the viewport of the chamber in a plasmaprocess, and thus be used to monitor a plasma state inside the chamber.More specifically, the microwave probe 100 may be coupled to an outersurface of the viewport mounted on the chamber in such a manner that themicrowave probe 100 contacts the outer surface of the viewport, wherebythe microwave probe 100 can be easily coupled to the chamber without achange in shape of the viewport. In addition, the microwave probe 100 isnon-invasively coupled to the outside of the chamber, whereby themicrowave probe 100 itself does not affect the plasma state inside thechamber. Therefore, using the non-invasive microwave probe 100, amicrowave is applied into the chamber, and signals generated inside thechamber are received, whereby the plasma state inside the chamber can beaccurately detected and monitored. A principle of detecting andmonitoring the plasma state inside the chamber using the microwave probe100 will be described below in more detail with reference to FIG. 11.

FIG. 2A is a perspective view of a microwave probe according to anexample embodiment of the inventive concept, FIG. 2B is a plan view ofthe microwave probe when the microwave probe is viewed from a head sidetowards a connector, FIG. 2C is a sectional view of the microwave probeincluding the connector, and FIG. 2D is a plan view of the microwaveprobe when the microwave probe is viewed from a connector side towardsthe head after a body, the head, and the connector are removed from themicrowave probe. In the interest of brevity, details which have beendescribed above with reference to FIGS. 1A and 1B may be only brieflydescribed or omitted.

Referring to FIGS. 2A to 2D, a microwave probe 100 a according to thepresent example embodiment may differ from the microwave probe 100 ofFIGS. 1A and 1B in that the microwave probe 100 a further includes aground cover 140. Specifically, the microwave probe 100 a according tothe present example embodiment may further include the ground cover 140surrounding a body 110 and a head 120.

As shown in FIGS. 2A to 2D, the ground cover 140 may have a rectangularframe structure with one side closed such that a rim or outer sidewallof the ground cover 140 protrudes or extends from a base of the groundcover 140 to surround the body 110 and the head 120. A through-hole H1may be formed in a central portion of the ground cover 140, and the body110 may extend through the through-hole H1 to be connected to aconnector 130 external to the ground cover 140. In some cases, thethrough-hole H1 is formed to have a larger size in the ground cover 140,and the connector 130 may be inserted into the through-hole H1.

The rim of the ground cover 140 may be brought into tight contact with awall of a chamber (200 in FIG. 15) to be coupled (e.g., by a fastenersuch as a screw) to the chamber. Thus, a screw hole S may be formed in aportion of the ground cover 140. Of course, in the ground cover 140, astructure for hook coupling, wedge coupling, snap coupling, or the likemay be formed instead of a structure for screw coupling. As shown inFIG. 8A, when the ground cover 140 is coupled to a wall 210 of thechamber 200, a surface of the head 120 may contact an outer surface of aviewport 220 of the chamber 200.

The ground cover 140 may include a conductive material, for example, ametal such as Cu, Al, and the like. The overall ground cover 140 may bea metal, or only a surface of the ground cover 140 may be a metal. Theground cover 140 may maintain a grounded state in a plasma process. Theground cover 140 alone may be grounded by directly connecting the groundcover 140 to a ground, and the ground cover 140 and the wall of thechamber may be grounded together by coupling the ground cover 140 to thewall of the chamber connected to a ground.

The ground cover 140 in a grounded state can block radiation of plasmalight from the viewport of the chamber, and prevent a noise external tothe microwave probe 100 a from entering or flowing into the head 120.Due to the presence of the ground cover 140, a reception efficiency ofthe head 120 for signals generated inside the chamber can be improved.Thus, measurement sensitivity of a surface wave resonant frequency canbe improved. In addition, as described above, the body 110 includes theinsulation covering layer 114, whereby the external noise can beprevented from entering or flowing in the metal layer 112. Further, thehead 120 may be formed in a thin film disk shape that contacts theviewport of the chamber, thereby further improving the receptionefficiency of the head 120.

As a result, the microwave probe 100 a according to the present exampleembodiment includes the body 110 including the insulation covering layer114, the disk-shaped head 120, and the ground cover 140 which canmaintain a grounded state while covering the body 110 and the head,thereby maximizing a reception efficiency for signals generated insidethe chamber, for example, measurement sensitivity for a surface waveresonant frequency.

FIGS. 3A and 3B are a plan view and a sectional view of a microwaveprobe according to an example embodiment of the inventive concept. FIG.3A is a plan view of the microwave probe when the microwave probe isviewed from a head side towards a connector. In the interest of brevity,details which have been described above with reference to FIGS. 1A to 2Dmay be only briefly described or omitted.

Referring to FIGS. 3A and 3B, a microwave probe 100 b according to thepresent example embodiment may differ from the microwave probe 100 a ofFIG. 2A in that the microwave probe 100 b further includes a filter 150.In addition, a head 120 a of the microwave probe 100 b may have an areathat is different from the area of the head 120 of the microwave probe100 a of FIG. 2A.

In the microwave probe 100 b, the head 120 a may have a second diameterD2, and the second diameter D2 may be less than the first diameter D1 ofthe head 120 of the microwave probe 100 or 100 a of FIG. 1A or 2A. Forexample, the second diameter D2 of the head 120 a may range from about 2cm to about 3 cm. If a viewport (see the reference numeral 220 in FIG.15) of a chamber (see the reference numeral 200 in FIG. 15) has adiameter of about 5 cm, the head 120 a may have a second diameter D2that is 75% or less of the diameter of the viewport.

As such, if the head 120 a has a relatively small area, when themicrowave probe 100 b is coupled to the chamber, an outer portion of theviewport may not contact the head 120 a and may be exposed. In a plasmaprocess, plasma light may be radiated through the exposed portion of theviewport.

In a plasma process, a plasma state inside the chamber may be directlyconfirmed by an eye in some cases. Here, the outer portion of theviewport, which does not contact the head 120 a and is exposed, may beused to confirm the plasma state. Plasma light may include ultra-violet(UV) light which can damage eyesight or a skin. Therefore, a filter toblock UV light may be desirable.

The microwave probe 100 b according to the present example embodimentmay include the filter 150, for example, a UV filter capable of blockingUV light. The filter 150 may have a shape surrounding an outer portionof the head 120 a. Specifically, the filter 150 may have a circular diskshape in which a central portion is empty (e.g., a ring shape). The head120 a may be inserted into the central portion of the filter 150, andthus be surrounded by the filter 150. For example, the central portionof the filter 150 may have a circular shape like the head 120 a, and thecentral open portion may have an area that is almost equal to orslightly greater than an area of the head 120 a.

As shown in FIGS. 9A and 9B, the filter 150 may have a shape and a sizethat are similar to those of the viewport. Thus, the filter 150 cancover the outer portion of the viewport, which does not contact the head120 a. In some cases, although the filter 150 may have a smaller sizethan the viewport, the filter 150 may have a larger size than a windowregion (see the reference numeral VPw in FIG. 9B) of the viewport,through which light passes.

The filter 150 may be included in or on the microwave probe 100 b in astate of being coupled to a ground cover 140 via an adhesive or thelike. In addition, if the viewport is formed in a circular recessedstructure on the chamber, the filter 150 may be inserted into therecess-structured viewport separately from the ground cover 140, andwhen the microwave probe 100 b is coupled to the chamber, the filter 150may contact the ground cover 140 to be included in or on the microwaveprobe 100 b.

The microwave probe 100 b according to the present example embodimentincludes the relatively small head 120 a and the filter 150 surroundingthe head 120 a, whereby a plasma state can be confirmed by an eyethrough the viewport at an outer side of the head 120 a while signalscan be received through the head 120 a. In addition, a UV filterblocking UV light is used as the filter 150, thereby protecting an eyefrom UV light. For reference, a window portion, through which light canpenetrate, may be formed in a portion of the ground cover 140, and aplasma state may be confirmed using the window portion. In addition, insome cases, a plasma state may be confirmed while the ground cover 140is separated from the microwave probe 100 b.

FIGS. 4A and 4B are a perspective view and a plan view of a microwaveprobe according to an example embodiment of the inventive concept, andFIG. 4B is a plan view of the microwave probe when the microwave probeis viewed from a head side towards a connector. In the interest ofbrevity, details which have been described above with reference to FIGS.1A to 2D may be only briefly described or omitted.

Referring to FIGS. 4A and 4B, a microwave probe 100 c according to thepresent example embodiment may differ from the microwave probe 100 a ofFIG. 2A in terms of a shape of a ground cover 140 a. For example, in themicrowave probe 100 c, the ground cover 140 a may have a circular framestructure with one side closed. In addition, a rim or sidewall of theground cover 140 a may protrude or extend from a base of the groundcover 140 a to surround a body 110 and a head 120.

Fastener holes such as screw holes S for screw coupling may be formed inthe rim of the ground cover 140 a. Of course, a structure for hookcoupling, wedge coupling, snap coupling, or the like may be formed inthe ground cover 140 a instead of a structure for screw coupling.Generally, since a viewport (220 in FIG. 220) of a chamber (200 in FIG.15) has a circular shape in most cases, the ground cover 140 a may beformed in a circular shape to symmetrically cover the viewport.

In the microwave probe 100 c, the shape of the ground cover 140 a is notlimited to the circular shape. For example, the ground cover 140 a mayhave various shapes, such as an ellipse, polygon, and the like, based onthe shape of the viewport.

FIG. 5 shows plan views of various shapes of head surfaces of microwaveprobes according to example embodiments of the inventive concept. In theinterest of brevity, details which have been described above withreference to FIGS. 1A and 1B may be only briefly described or omitted.

Referring to FIG. 5, a head 120 of FIG. 5(a) is a head having the mostfundamental structure. The head 120 may be formed in a circular flatplate structure, and may not include any pattern on a surface thereof.For example, patterns such as grooves may not be formed on the surfaceof the head 120, which contacts a viewport (220 in FIG. 8A) of a chamber(200 in FIG. 8A), and the surface of the head 120 may be maintained in asmooth state.

A head 120 b of FIG. 5(b) may include irregular patterns on a surfacethereof. For example, a large number of grooves 122 having a straightline or curve shape may be formed on the surface of the head 120 b. Thegrooves 122 are formed on the surface of the head 120 b, such that anefficiency of microwave application and/or signal reception through thehead 120 b can be improved.

A head 120 c of FIG. 5(c) may include a spiral pattern on a surfacethereof. For example, a spiral groove 122 a may be formed on the surfaceof the head 120 c. The spiral groove 122 a is formed on the surface ofthe head 120 c, such that an efficiency of microwave application and/orsignal reception through the head 120 c can be improved.

A head 120 d of FIG. 5(d) may include a large number of concentriccircular patterns on a surface thereof. For example, a large number ofconcentric circular grooves 122 b may be formed on the surface of thehead 120 d. The concentric circular grooves 122 b are formed on thesurface of the head 120 d, such that an efficiency of microwaveapplication and/or signal reception through the head 120 d can beimproved.

Although the straight line or curve-shaped grooves, the spiral groove,and the concentric circular grooves on the surface of the head have beendescribed above as examples, shapes of patterns on the surface of thehead are not limited thereto. For example, to improve microwaveapplication and/or signal reception efficiencies of the head, patternshaving a wide variety of shapes may be formed on the surface of thehead.

A head 120 e of FIG. 5(e) may have an elliptical flat plate structure,and a head 120 f of FIG. 5(f) may have a rectangular flat platestructure. Of course, the shape or structure of the head is not limitedto the flat plate structures set forth above. For example, the head mayhave various shapes such as triangular flat plates, pentagonal flatplates, and the like.

In the microwave probe according to the present example embodiment, theshape of the head may be variously changed in consideration of a shapeof the viewport with which the head is brought into contact, orimprovement in efficiencies of microwave application and/or signalreception. In addition, in the microwave probe according to the presentexample embodiment, the structure of the head is not limited to flatplates. For example, in some cases, the head may have a probe shapeinstead of a flat plate shape. In the head having a probe shape, insteadof separately forming the head, a portion of an end of the metal layer112 of the body 110 may act as the head.

FIG. 6 shows perspective views of various shapes of bodies of microwaveprobes according to example embodiments of the inventive concept. In theinterest of brevity, details which have been described above withreference to FIGS. 1A and 1B may be only briefly described or omitted.

Referring to FIG. 6, FIG. 6(a) shows a metal layer 112 of a body 110,and the metal layer 112 may have a circular pillar or cylindrical shapeextending in one direction. As described above, the metal layer 112 mayinclude a metal having good conductivity, for example, Cu, Al, or thelike. The metal layer 112 may have a thickness of about 1 mm and alength of a few centimeters. Of course, the thickness and the length ofthe metal layer 112 are not limited to the numerical values set forthabove.

FIG. 6(b) shows a metal layer 112 a having a rectangular or quadrangularpillar shape, and the metal layer 112 a may have a thickness and alength, which are similar to those of the metal layer 112 of FIG. 6(a).For reference, the thickness may refer to a diameter when the metallayer is a circular pillar, and the thickness may refer to a length of ashorter side when the metal layer is a rectangular pillar. Although thecircular pillar and quadrangular pillar shapes are illustrated asexamples of structures of the metal layers 112, 112 a in FIGS. 6(a) and6(b), the structure of the metal layer is not limited thereto. Forexample, the metal layer may also be formed in an elliptical pillarshape or a polygonal pillar shape other than a quadrangular pillarshape. The metal layer 112 of FIG. 6(a) itself and the metal layer 112 aof FIG. 6(b) itself may respectively constitute bodies 110, 110 awithout insulation covering layers on outer sides thereof.

FIG. 6(c) shows a structure of a fundamental body 110, and the body 110may include an inner metal layer 112 and an outer insulation coveringlayer 114. The metal layer 112 may have a circular pillar shape like themetal layer 112 of FIG. 6(a). Of course, the metal layer 112 may have aquadrangular pillar shape like the metal layer 112 a of FIG. 6(b), ormay have other polygonal pillar shapes. The insulation covering layer114 surrounds the metal layer 112, and includes an insulating materialfor insulating the metal layer 112, as described above.

FIG. 6(d) shows a body 110 b having a coaxial cable structure. The body110 b may include an inner metal layer 112-1, an inner insulating layer114-1, an outer metal layer 112-2, and an outer insulating layer 114-2.The inner metal layer 112-1 and the outer metal layer 112-2 mayconstitute a metal layer 112 b, and the inner insulating layer 114-1 andthe outer insulating layer 114-2 may constitute an insulation coveringlayer 114 a.

The coaxial cable structure may be used when a frequency of atransferred signal is high. More specifically, since the coaxial cableexhibits low attenuation of a signal at up to a high frequency, thecoaxial cable is suitable for broadband transmission. In addition, thecoaxial cable can exhibit low leakage or loss of a signal due to thepresence of the outer metal layer 112-2. The inner insulating layer114-1 may generally include polyethylene, and may include a circularplate-shaped spacer when the cable is thick. In addition, when used inthe cable for the purpose of a high temperature, the inner insulatinglayer 114-1 may include teflon. Since materials, signal transferproperties, and the like of the coaxial cable are known in the art,further details thereof will be omitted herein.

The bodies of the microwave probes 100, 100 a, 100 b, 100 c according tothe present embodiment may have a coaxial cable structure like the body110 b of FIG. 6(d). Thus, the bodies of the microwave probes 100, 100 a,100 b, 100 c can stably transfer signals of relatively high frequencies.In addition, an external cable or wire (see the reference numeral 310 inFIG. 8A) connected to the connectors (130 in FIG. 1A, and the like) mayalso be formed in a coaxial cable structure. Such a coaxial cablestructure is mainly used for an RF cable which transfers RF signals.

FIGS. 7A and 7B are sectional views of microwave probes according toexample embodiments of the inventive concept. In the interest ofbrevity, details which have been described above with reference to FIGS.1A to 6 may be only briefly described or omitted.

Referring to FIG. 7A, a microwave probe 100 d according to the presentexample embodiment may differ from the microwave probe 100 of FIG. 1A interms of a structure of a head 120 b. In the microwave probe 100 d, thehead 120 b may have a considerably smaller area. For example, a thirddiameter D3 of the head 120 b may be not more than three times a firstthickness T1 of a body 110. In some cases, the third diameter D3 of thehead 120 b may be almost or substantially the same as the firstthickness T1 of the body 110. Furthermore, the third diameter D3 of thehead 120 b may be almost or substantially the same as a thickness of ametal layer 112 of the body 110. When the third diameter D3 of the head120 b is substantially the same as the thickness of the metal layer 112of the body 110, a portion of the metal layer 112 may be used as thehead without separately forming the head, and the head 120 b may have aprobe shape.

When a viewport 220 b has a groove or channel in a central portionthereof, the head 120 b of the microwave probe 100 d may be sized to beinserted into and coupled to the groove of the viewport 220 b, as shownin FIG. 12A or 12B. In addition, an area of the head 120 b may vary withan area of a bottom or end surface of the groove of the viewport 220 b.For example, the area of the head 120 b may be substantially the same asthe area of the bottom surface of the groove of the viewport 220 b.Thus, if an area of the groove of the viewport 220 b is similar to anarea of the body 110 of the microwave probe 100 d, the head 120 b mayhave almost or substantially the same diameter as a cross section of thebody 110.

Referring to FIG. 7B, a microwave probe 100 e according to the presentexample embodiment may differ from the microwave probe 100 a of FIG. 2Ain terms of a structure of a head 120 b. In the microwave probe 100 e,the head 120 b may have a considerably smaller area like the microwaveprobe 100 d of FIG. 7A. When a viewport 220 b has a groove in thecentral portion thereof, the microwave probe 100 e may also provide astructure which can be easily coupled to the viewport 220 b.Specifically, the head 120 b may be inserted into the groove of theviewport 220 b, and a ground cover 140 may be coupled to an outer wallof a chamber through fastener (e.g., screw) coupling or the like, suchthat the microwave probe 100 e may be coupled to the viewport 220 b ofthe chamber.

FIGS. 8A and 8B are a sectional view and a plan view of the microwaveprobe of FIG. 2A, which is coupled to a chamber. FIG. 8B is the planview of the microwave probe of FIG. 2A when the microwave probe of FIG.2A is viewed from a connector side towards the head, and the connector,the ground cover, the chamber wall, and the like are omitted in FIG. 8Bfor clarity. In the interest of brevity, details which have beendescribed above with reference to FIGS. 1A to 7B may be only brieflydescribed or omitted.

Referring to FIGS. 8A and 8B, the microwave probe 100 a according to thepresent example embodiment may be coupled to a viewport 220 of a chamber200. The chamber 200 may include a wall 210 such as an outer wall forisolating an inside of the chamber from an outside of the chamber, andmay include a through-hole H2 penetrating through the wall 210 in aportion to which the viewport 220 is mounted. The viewport 220 may becoupled to the wall 210 to cover or fill the through-hole H2. Since theviewport 220 also serves to isolate the inside of the chamber from theoutside of the chamber, the viewport 220 may be included in the wall ofthe chamber.

Since the viewport 220 includes a material such as quartz (SiO₂),sapphire (Al₂O₃), or the like, plasma light inside the chamber may beradiated to the outside of the chamber through the viewport 220. Thus,the inside of the chamber or plasma light may be visually observedthrough the viewport 220, or an optical apparatus capable of detectingplasma light may be mounted on the viewport 220, thereby detectingplasma light through the optical apparatus.

As shown in FIG. 8B, the viewport 220 may include a window region VPwcorresponding to the through-hole H2 and an outer region VPo. The windowregion VPw may be a region through which plasma light radiated throughthe through-hole H2 is transmitted, and the outer region VPo may be aregion which is brought into contact with and coupled to the wall 210 ofthe chamber 200. In other words, the first diameter (D1 in FIG. 2C) ofthe head 120 may be almost the same as or slightly less than a fourthdiameter D4 of the window region VPw. In some cases, the first diameterD1 of the head 120 may be greater than the fourth diameter D4 of thewindow region VPw. As such, the head 120 may be coupled to the viewport220 to cover the overall window region VPw, thereby improving signaltransfer properties of the microwave probe 100 a. In particular, sinceplasma generated inside the chamber 200 is directly transferred to thewindow region VPw of the viewport 220 through the through-hole H2, thehead 120 can more accurately detect a plasma state.

The ground cover 140 may be coupled to the wall 210 of the chamber 200through fastener (e.g., screw) coupling or the like. As shown in FIG.8A, an outer surface of the wall 210 of the chamber 200 may be in thesame plane as an outer surface of the viewport 220. Thus, the groundcover 140 may be coupled to the chamber 200 to contact both the outersurface of the viewport 220 and the outer surface of the wall 210 of thechamber 200. In some cases, the outer surface of the viewport 220 may becloser to the inside of the chamber 200 than the outer surface of thewall 210 of the chamber 200. With this structure, the ground cover 140may be coupled to the chamber 200 to contact only the wall 210 of thechamber 200.

For reference, the wall 210 of the chamber 200 may generally include ametal material, and may be maintained in a grounded state to blocknoises from the outside of the chamber 200 in a plasma process. Aninsulating liner 230 may be arranged on an inner side or surface of thewall 210 of the chamber 200. The insulating liner 230 may protect thewall 210 of the chamber 200 and cover metal structures protruding fromthe wall 210, thereby preventing arcing inside the chamber. Theinsulating liner 230 may include ceramic, quartz, or the like. Forexample, the insulating liner 230 may have a structure in which yttriumoxide (Y₂O₃) is coated onto sapphire (Al₂O₃).

FIGS. 9A and 9B are a sectional view and a plan view of the microwaveprobe of FIG. 3A, which is coupled to a chamber. FIG. 9B is the planview of the microwave probe of FIG. 3A when the microwave probe of FIG.3A is viewed from a connector side towards the head, and the connector,the ground cover, the chamber wall, and the like are omitted in FIG. 9Bfor clarity. In the interest of brevity, details which have beendescribed above with reference to FIGS. 1A to 8B may be only brieflydescribed or omitted.

Referring to FIGS. 9A and 9B, the microwave probe 100 b according to thepresent example embodiment may also be coupled to the viewport 220 ofthe chamber 200. As described above, the head 120 a of the microwaveprobe 100 b may be smaller than the head 120 of the microwave probe 100a of FIG. 2A, and the microwave probe 100 b may further include thefilter 150 outside or around the head 120 a. Thus, the microwave probe100 b may be coupled to the viewport 220 of the chamber 200 such thatthe outer surface of the viewport 220 is covered with the head 120 a andthe filter 150.

More specifically, the head 120 a may cover a portion of the windowregion VPw of the viewport 220, and the filter 150 may cover anotherportion of the window region VPw, which is not covered with the head 120a, and the outer region VPo. In some cases, the filter 150 may have asmaller size in shape than the viewport 220, and thus may cover only aportion of the outer region VPo or may not cover the outer region VPo.The filter 150 covers the exposed window region VPw, which is notcovered with the head 120 a, and thus may block UV light and the likeamong plasma light. Thus, the outer region VPo, through which plasmalight is not transmitted, may not be covered or entirely covered.

In the microwave probe 100 b, the ground cover 140 may also be coupledto the wall 210 of the chamber 200 through fastener (e.g., screw)coupling or the like. As shown in FIG. 9A, the outer surface of the wall210 of the chamber 200 may be in the same plane as an inner surface ofthe filter 150. Thus, the ground cover 140 may be coupled to the chamber200 to contact both the inner surface of the filter 150 and the outersurface of the wall 210 of the chamber 200. As shown in FIG. 8A, theouter surface of the wall 210 of the chamber 200 may be in the sameplane as the outer surface of the viewport 220. In this structure, thefilter 150 may have a smaller size in external shape (e.g., smallerdiameter) than the viewport 220, and the ground cover 140 may contactboth the outer surface of the viewport 220 and the outer surface of thewall 210 of the chamber 200. In this case, the ground cover 140 maysurround the head 120 a and the filter 150.

FIG. 10 is a plan view of the microwave probe of FIG. 2A, which iscoupled to a chamber, when the microwave probe of FIG. 2A is viewed froma connector side towards the head, and the connector, the ground cover,the chamber wall, and the like are omitted in FIG. 10 for clarity. Inthe interest of brevity, details which have been described above withreference to FIGS. 1A to 9B may be only briefly described or omitted.

Referring to FIG. 10, the microwave probe 100 a according to the presentexample embodiment may have the same structure as the microwave probe100 a of FIG. 8A. However, a viewport 220 a to which the microwave probe100 a is coupled may differ in shape from the viewport 220 of FIG. 8B.For example, the viewport 220 a may have a rectangular or squarestructure as shown in FIG. 10. The viewport 220 a may include a windowregion VPw and an outer region VP′o. Since a shape of the window regionVPw corresponds to the shape of the through-hole (H2 in FIG. 8A), thewindow region VPw may be substantially the same as the window region VPwof the viewport 220 of FIG. 8B. However, due to a difference in theshape of the viewport 220 a, the outer region VP′o may differ in shapefrom the outer region VPo of the viewport 220 of FIG. 8B.

As described above, since the outer region VP′o is a region to which thewall 210 of the chamber 200 is coupled, the selection of the shape ofthe outer region VP′o may not have much consequence. Thus, the viewport220 a is not limited to circular or rectangular shapes, and may have apolygonal shape other than elliptical or rectangular shapes, forexample.

FIG. 11 is a conceptual diagram for explaining a method of detecting aplasma state inside a chamber using a microwave probe according to anexample embodiment of the inventive concept.

Referring to FIG. 11, a wafer 500 is disposed on an electrostatic chuck240 inside the chamber 200, and plasma P is generated by injecting aprocess gas and applying RF power into the chamber, thereby performing aplasma process using the plasma P. For example, the plasma process mayinclude etching, deposition, diffusion, surface treatment, novelmaterial synthesis processes, and the like. The plasma process,particularly a semiconductor plasma process will be described in moredetail in descriptions related to FIG. 15. The microwave probesaccording to the example embodiments of the inventive concept, forexample, the microwave probe 100 a of FIG. 2A may be coupled to theviewport 220 of the chamber 200. In addition, the microwave probe 100 amay be connected to the network analyzer 300 through the external cableor wire 310 connected to the connector (see the reference numeral 130 inFIG. 2A).

The network analyzer 300 generates a microwave, and transfers themicrowave to the microwave probe 100 a through the external wire 310,thereby applying the microwave into the chamber 200 through the head(120 in FIG. 2A). The network analyzer 300 may be a commercial networkanalyzer. Since a resonant frequency of several hundred mega hertz (MHz)to a few giga hertz (GHz) is generally observed in a semiconductorplasma process, the network analyzer 300 can be used for thesemiconductor plasma process as long as the network analyzer 300 cangenerate a microwave suitable for those conditions. The microwave may betransferred from a signal transmission port of the network analyzer 300to the microwave probe 100 a through the external wire 310.

The microwave M_(in) that is input into the chamber 200 resonates at aspecific frequency. Resonance may be sensed through a change in ameasured value of a reflection coefficient S11. That is, as shown in agraph inside the network analyzer 300 at the left side in FIG. 11,specific peak values of a reflection coefficient S11 of an appliedsignal are observed, and frequencies corresponding to those peak valuesmay be resonant frequencies f_(r). Since frequencies other than aspecific resonant frequency are fully reflected, the reflectioncoefficient S11 is almost 1.

Such a resonant frequency may be explained by resonance of a surfacewave, and a resonant frequency of the surface wave is physicallyassociated with a density of electrons generated in plasma. Thus, if theresonant frequency is known, the density of the electron generated inthe plasma can be confirmed. A correlation between the resonantfrequency of the surface wave and the electron density in the plasma canbe described as follows.

First, an oscillation frequency (f_(pe)) of the plasma can berepresented by Equation (1).

f _(pe)=½π·(e ² N _(e)/∈₀ m _(e))^(1/2)  Equation (1)

Here, e is a quantity of electric charge of an electron, N_(e) is thenumber of electrons per unit volume (cm³), that is, an electron density,∈₀ is a dielectric constant in vacuum, and m_(e) is mass of an electron.e, ∈₀, and m_(e) are constants, and if values thereof are substituted,Equation (1) can be rearranged as Equation (2).

f _(pe) (Hz)⇄8980·(N _(e) (cm⁻³))^(1/2)  Equation (2)

The oscillation frequency (f_(pe)) of the plasma is proportional to anabsorption frequency (f_(abs)) of the surface wave, that is, theresonant frequency of the surface wave. In other words, the oscillationfrequency (f_(pe)) of the plasma and the absorption frequency (f_(abs))of the surface wave may have a relation of Equation (3).

f _(pe) ∝f _(abs)->f _(pe) =k·f _(abs)  Equation (3)

Here, a proportional factor k is not a fixed value, but a value thatvaries with the viewport, the probe structure, measurement conditions,and the like. In other words, it is actually complicated toquantitatively determine the relation between the oscillation frequency(f_(pe)) of the plasma and the resonant frequency of the surface wave.However, the k value is experimentally and/or statistically determined,and the k value can then be utilized for the purpose of sensing aqualitative state change in monitoring for a plasma process.

Finally, if the resonant frequency of the surface wave, that is, theabsorption frequency (f_(abs)) of the surface wave is detected, and thek value is experimentally and/or statistically determined, the electrondensity (N_(e)) of the plasma can be found by substituting Equation (2),which is an equation relating to the oscillation frequency (f_(pe)) ofthe plasma, into Equation (3). If a signal of the resonant frequency isactually measured by the network analyzer 300, the measured resonantfrequency signal is transferred to a computer for analysis, and thecomputer finally calculates the electron density of the plasma using aanalysis program. For example, the analysis program may be a program forcalculating the electron density of the plasma using Equations (1) to(3), the value of the proportional factor k, and the like. In addition,the value of the proportional factor k may be experimentally and/orstatistically determined based on the viewport, the probe structure,measurement conditions, and the like according to a corresponding plasmaprocess. If the electron density of the plasma is calculated, a density,a state, and the like of the plasma in the plasma process can beaccurately diagnosed.

The calculated electron density of the plasma may indicate a plasmastate in the vicinity of the viewport 220 inside the chamber 200. Inother words, the resonant frequency may be detected during the plasmaprocess using the microwave probe 100 a and the network analyzer 300,thereby sensing a plasma state in the vicinity of the wall (seereference numeral 210 in FIG. 8A) of the chamber 200, on which theviewport 220 is mounted, in real time. Finally, in the plasma process,the microwave probe 100 a according to the present example embodimentcan contribute to optimizing the plasma process by monitoring whetherthere is a problem in the plasma state in real time.

For reference, in an existing method of monitoring a plasma process, aprobe is directly inserted into a chamber in an invasive manner. Suchdirect insertion of the probe cause process gases in use and generatedreaction species to directly contact a surface of the probe during theplasma process, and thus has an influence on a situation of the plasmaprocess. Thus, a distorted situation of the plasma process is monitoredinstead of an ideal situation thereof due to the invasive probe. Inconclusion, the method of monitoring the plasma process by directlyinserting the probe into the chamber is not suitable for industrialenterprises, and is limited to use for advanced research and developmentin university institutes, and the like.

On the other hand, each of the microwave probes 100, 100 a to 100 eaccording to the example embodiments of the inventive concept isnon-invasively coupled to the viewport 220 of the chamber 200, therebynot affecting the plasma state inside the chamber 200. In addition, eachof the microwave probes 100, 100 a to 100 e may include the body 110including the insulation covering layer 114, and the disk-shaped head120, thereby optimizing microwave application and/or a measurementsensitivity to signals generated inside the chamber. Further, each ofthe microwave probes 100, 100 a to 100 e may include the ground cover140 which can maintain a grounded state while covering the body 110 andthe head 120, thereby maximizing the measurement sensitivity to thesignals by maximizing a signal-to-noise ratio (SNR).

FIGS. 12A and 12B are sectional views of microwave probes according toexample embodiments of the inventive concept, which are coupled todifferently-shaped viewports included in chambers. In the interest ofbrevity, details which have been described above with reference to FIGS.1A to 10 may be only briefly described or omitted.

Referring to FIG. 12A, a microwave probe 100 e according to the presentexample embodiment may be substantially the same as the microwave probe100 e of FIG. 7B. Thus, the microwave probe 100 e may include the body110, the head 120 b, the connector 130, and the ground cover 140, andthe head 120 may have a relatively small area. For example, the thirddiameter (D3 in FIG. 7A) of the head 120 b may be not more than threetimes the first thickness (T1 in FIG. 7A) of the body 110. Of course,the diameter of the head 120 b is not limited thereto.

The viewport 220 b of the chamber 200 a may have a structure in whichthe viewport 220 b is inserted into a through-hole H3 in the wall 210 aof the chamber 200 a, and may include a groove or channel G in thecentral portion thereof. The groove G of the viewport 220 b may have acylindrical shape. Of course, the groove G of the viewport 220 b is notlimited to the cylindrical shape. A fifth diameter D5 of the groove G ofthe viewport 220 b may be similar to or slightly greater than the thirddiameter D3 of the head 120 b. The microwave probe 100 e may be coupledto the chamber 200 a such that the body 110 and the head 120 b areinserted into the groove G of the viewport 220 b.

As shown in FIG. 12A, the outer surface of the viewport 220 b and theouter surface of the wall 210 a of the chamber 200 a may be in the sameplane, and the ground cover 140 may be coupled to the chamber 200 a tocontact both the outer surface of the viewport 220 b and the outersurface of the wall 210 a of the chamber 200 a. Of course, the outersurface of the viewport 220 b may be closer to the inside of the chamber200 a than the outer surface of the wall 210 a of the chamber 200 a. Inthis case, the ground cover 140 may contact only the outer surface ofthe wall 210 a of the chamber 200 a. Of course, although not shown inFIG. 12A, the insulating liner 230 may be arranged on the inner side orsurface of the wall 210 a of the chamber 200 a as in FIG. 8A or 9A.

Referring to FIG. 12B, a microwave probe 100 f according to the presentexample embodiment may differ from the microwave probe 100 e of FIG. 12Ain that the microwave probe 100 f further includes an outer cover layer115. For example, the microwave probe 100 f may further include theouter cover layer 115 surrounding the body 110. The outer cover layer115 may have a cylindrical tube shape, and have a diameter that is aboutor almost the same as the fifth diameter D5 of the groove G of theviewport 220 b. The outer cover layer 115 may include a metal such asCu, or Al. However, the outer cover layer 115 may also include anon-metal such as a plastic. In addition, the outer cover layer 115 mayinclude a non-metal such as a plastic, and a metal only on an outersurface thereof.

When the microwave probe 100 f is coupled to the viewport 220 b of thechamber 200 a, the outer cover layer 115 is inserted into the groove Gof the viewport 220 b to be firmly secured therein. Since the outercover layer 115 is secured to the groove G, trembling, vibration,deformation, or the like of the head 120 b and the body 110 can besuppressed. In addition, if the outer cover layer 115 includes a metal,the body 110 and the outer cover layer 115 may form a coaxial cable-likestructure, and thus contribute to improved signal transfer properties ofthe microwave probe 100 f.

FIGS. 13A and 13B are graphs depicting reflection coefficients alongwith frequencies while a pressure and applied power inside a chamber arechanged, using a microwave probe according to an example embodiment ofthe inventive concept. An x axis represents a frequency, and a y axisrepresents a reflection coefficient S11. FIG. 13A is a graph obtained bychanging the applied power while a pressure of argon (Ar) gas inside thechamber is fixed at 1 mTorr, and FIG. 13B is a graph obtained bychanging the pressure of Ar gas while the applied power is fixed at 3kW.

Referring to FIG. 13A, it can be seen that a peak value of thereflection coefficient S11 increases with increasing applied power. Thatis, it can be seen that a resonant frequency increases with increasingpower. The increase of the resonant frequency may mean an increase of aoscillation frequency (f_(pe)) of plasma, and the increase of theoscillation frequency (f_(pe)) of the plasma may finally mean anincrease of an electron density of the plasma. Thus, it can be seen thatthe electron density of the plasma increases with increasing power. Thereason for this may be that since energy, which is transferred toprocess gases, for example, Ar gas in the chamber, increases withincreasing applied RF power, kinetic energy and collision frequency ofthe process gases increase, thereby increasing a possibility of plasmageneration. As described above, it can be confirmed that sincefrequencies other than the resonant frequency are almost fullyreflected, the reflection coefficient S11 is close to 1.

Referring to FIG. 13B, it can be seen that the peak value of thereflection coefficient S11 increases with increasing pressure in thechamber. That is, it can be seen that the resonant frequency increaseswith increasing pressure.

Like the above conclusion that the increase of the resonant frequencydue to the increase of the power leads to the increase of the electrondensity of the plasma, the increase of the resonant frequency due to theincrease of the pressure may also lead to the increase of the electrondensity of the plasma. The increase of the electron density of theplasma due to the increase of the pressure may be caused by the factthat since the increase of the pressure leads to an increase of anamount of the process gases, for example, Ar gas in the chamber, thecollision frequency of the process gases increase, thereby increasing apossibility of plasma generation.

FIG. 14 is a graph depicting a correlation between an oscillationfrequency of plasma and an absorption frequency of a surface wavedepending upon a pressure change. An x axis represents the oscillationfrequency (f_(pe)) of the plasma, and a y axis represents the absorptionfrequency (f_(abs)) of the surface wave, that is, a resonant frequencyof the surface wave. Measurement may be performed in a chamber, on whicha round viewport is mounted, under Ar discharge.

Referring to FIG. 14, it can be seen that, for each pressure, there isan approximate one dimensional graph relation (e.g., an approximatelinear relation) between the oscillation frequency (f_(pe)) of theplasma and the absorption frequency (f_(abs)) of the surface wave. Thus,a value of the proportional factor k of Equation (3) may be found basedon the graph of the relation between the oscillation frequency (f_(pe))of the plasma and the absorption frequency (f_(abs)) of the surfacewave. As described above, if the value of the proportional factor k isfound and the resonant frequency is detected, an electron density of theplasma can be calculated.

FIG. 15 is a schematic configuration diagram of a plasma monitoringsystem including a microwave probe according to an example embodiment ofthe inventive concept. In the interest of brevity, details which havebeen described above with reference to FIGS. 1A to 12B may be onlybriefly described or omitted.

Referring to FIG. 15, a plasma monitoring system 1000 according to thepresent example embodiment may include a microwave probe 100 a, achamber 200, a network analyzer 300, RF power supplies 400-1, 400-2, gassupplying sources 600-1, 600-2, a pumping device 700, and a computer 800for analysis.

For example, the microwave probe 100 a may be the microwave probe 100 aof FIG. 2A. Of course, instead of the microwave probe 100 a of FIG. 2A,any one of the microwave probes 100, 100 b, 100 c, 100 d, 100 e, 100 faccording to the other example embodiments may be used for the plasmamonitoring system 1000 according to the present example embodiment. Astructure of the microwave probe may variously changed in considerationof a shape of a viewport 220 of the chamber, or improvement inefficiencies of microwave application and/or signal reception. Inaddition, considering that a head can greatly contribute to improvementin efficiencies of microwave application and/or signal reception, thehead may have various shapes as well as may include various-shapedpatterns on a surface thereof, which is brought into contact with theviewport 220 as described above with reference to FIG. 5.

The chamber 200 may be a chamber for a plasma process. For example, asshown in FIG. 15, the chamber 200 may be a chamber for inductivelycoupled plasma (ICP). Of course, the chamber 200 is not limited to thechamber for ICP. For example, the plasma monitoring system 1000according to the present example embodiment may employ various chamberssuch as a chamber for capacitively coupled plasma (CCP), a chamber forelectron cyclotron resonance (ECR) plasma, a chamber for surface waveplasma (SWP), a chamber for helicon wave plasma, a chamber for e-beamplasma, and the like. The chamber and peripheral devices may also becollectively referred to, as a plasma system, and the peripheral devicesmay slightly vary with a kind of chamber. For example, in the plasmamonitoring system 1000 according to the present example embodiment, thechamber 200 for ICP, the RF power supplies 400-1, 400-2, the gassupplying sources 600-1, 600-2, and the pumping device 700 may beconfigured for an ICP system.

For reference, plasma can be divided into low temperature plasma andthermal plasma according to temperatures. Low temperature plasma ismainly used for semiconductor processes such as semiconductorfabrication, metal and ceramic thin film fabrication, materialsynthesis, and the like, and thermal plasma is used for metal cutting,and the like. Low temperature plasma can be divided again intoatmospheric pressure plasma, vacuum plasma, next generation plasma, andthe like according to applications. An atmospheric pressure plasmatechnique refers to a technique of generating low temperature plasmawhile a pressure of a gas is maintained at 100 Torr to atmosphericpressure (760 Torr), and may be used for surface modification, displayflat panel cleaning, light sources for LCDs, and the like. A vacuumplasma technique refers to a technique of generating low temperatureplasma while a pressure of a gas is maintained at 100 Torr or less, andmay be used for dry etching, thin film deposition, PR ashing, ALDgrowth, and the like in semiconductor processes, and used for etching,thin film deposition, and the like with respect to a display flat panelin display processes. A next generation plasma technique may refer to atechnique of generating advanced concept low temperature plasma and/orgenerating low temperature plasma capable of being used for nextgeneration new technologies.

The chamber 200 may fundamentally include the wall 210, the viewport220, the electrostatic chuck (ESC) 240, and a shower head 250. Since thewall 210 and the viewport 220 have been described above with respect toFIGS. 8A and 8B, details thereof will not be repeated in the interest ofbrevity. The electrostatic chuck 240 is arranged in a lower portioninside the chamber 200, and a wafer 500 may be placed on an uppersurface of the electrostatic chuck 240 and secured thereto. Theelectrostatic chuck 240 may allow the wafer 500 to be secured theretousing electrostatic force. The shower head 250 is arranged in an upperportion inside the chamber 200, and may spray a process gas or the likeinto the chamber 200 through a plurality of spray holes.

The RF power supplies 400-1, 400-2 may include an upper RF power supply400-1 and a lower RF power supply 400-2. The upper RF power supply 400-1may include an RF generator 410-1, a matcher 430-1, and a coil 450. TheRF generator 410-1 generates RF power, and the matcher 430-1 stabilizesplasma by adjusting impedance. The matcher 430-1 is also referred to asa matching box. The coil 450 is spirally arranged on an upper side ofthe chamber 200, and generates a magnetic field inside the chamber by RFpower application. The magnetic field accelerates electrons or ionsinside the chamber to further accelerate plasma generation.

The lower RF power supply 400-2 may also include an RF generator 410-2and a matcher 430-2, and apply RF power to the wafer 500 instead of thecoil. In some cases, RF power may be applied to the wafer 500 via theelectrostatic chuck 240.

The gas supplying sources 600-1, 600-2 supply process gases required fora plasma process. Here, the process gases may refer to all gases, suchas a source gas, a reaction gas, a purge gas, and the like, required fora corresponding plasma process. Although the two gas supplying sources600-1, 600-2 are shown in FIG. 15, two or more gas supplying sources maybe included according to the kinds of process gases. The process gasesof the gas supplying sources 600-1, 600-2 are supplied to the showerhead 250 through gas supplying tubes, and sprayed into the chamber 200through the shower head 250. In some cases, a specific process gas ofthe gas supplying sources 600-1, 600-2 may be directly supplied into thechamber 200 through a gas supplying tube directly connected into thechamber 200.

The pumping device 700 may discharge gases inside the chamber 200 to theoutside of the chamber 200 through a vacuum pump or the like after aplasma process. In addition, the pumping device 700 may serve to adjusta pressure inside the chamber 200.

The network analyzer 300 is as described above with reference to FIG.11. The computer 800 for analysis may be a general personal computer(PC), a workstation, a supercomputer, or the like. An analysis program,which can calculate an electron density of plasma based on Equations (1)to (3), the proportional factor k, and the like, is installed in thecomputer 800 for analysis. Thus, the computer 800 for analysis mayreceive a detected resonant frequency that is input from the networkanalyzer 300, and calculate an electron density of plasma using theanalysis program. In addition, the computer 800 for analysis maydetermine whether there is a problem in a plasma state by comparing thecalculated electron density of the plasma with a pre-set referencevalue. Further, when there is a problem in the plasma state, thecomputer 800 for analysis may also analyze a cause thereof and suggestnew process conditions for a plasma process in question.

The plasma monitoring system 1000 according to the present exampleembodiment includes the microwave probe 100 a which is non-invasivelycoupled to the viewport 220 of the chamber 200, whereby the microwaveprobe 100 a does not affect the plasma state inside the chamber 200.Thus, the plasma monitoring system 1000 can precisely detect the plasmastate inside the chamber 200 using the microwave probe 100 a and thenetwork analyzer 300. In addition, the plasma monitoring system 1000includes the microwave probe 100 a which includes the body 110 includingthe insulation covering layer 114, the disk-shaped head 120, and theground cover 140 covering the body 110 and the head 120 and maintaininga grounded state, thereby optimizing and maximizing microwaveapplication and a measurement sensitivity to signals inside the chamber200. Thus, the plasma monitoring system 1000 accurately detects theresonant frequency, and accurately calculates the electron density ofthe plasma based on the detected resonant frequency, thereby preciselymonitoring whether there is a problem in the plasma state inside thechamber 200.

As described with reference to FIGS. 16 to 19, the plasma monitoringsystem 1000 according to the present example embodiment is used fordetermination of a time point of plasma stabilization, tool matchingbetween chambers, determination of a time point of preventivemaintenance (PM) for a chamber, sensing of in-process issues, and thelike, thereby significantly contributing to optimization of a plasmaprocess.

FIG. 16 is a graph showing a concept for determining a time point ofstabilization of plasma inside a chamber using a plasma monitoringsystem according to an example embodiment of the inventive concept. An xaxis represents a wafer number introduced into a chamber, a left y axisrepresents an electron density of plasma inside the chamber, and a righty axis represents an etch rate. The electron density of the plasma ismarked by a symbol ▪, and the etch rate is marked by a symbol ▾.

Referring to FIG. 16, when a plasma process is newly performed in thechamber (see the reference numeral 200 in FIG. 15) in an idle state, itis necessary to determine whether generated plasma reaches anappropriate state required for the plasma process in question. That is,before a wafer for devices is subjected to the plasma process, it isnecessary to determine a time point of plasma stabilization, that is, atime point of plasma back-up, and only after the time point of plasmastabilization, the wafer for devices can be subjected to the plasmaprocess.

Generally, dummy wafers are introduced into the chamber and subjected toa plasma process, followed by examining the dummy wafers, for example,etch rates for the dummy wafers, thereby determining whether plasmareaches an appropriate state. As such, in the existing method ofdetermining the time point of plasma stabilization, a large number ofdummy wafers, for example, one hundred or more dummy wafers may beconsumed, and a lot of time may be spent since the dummy wafers need tobe examined after the plasma process.

However, if the plasma monitoring system (1000 in FIG. 15) according tothe present example embodiment is used, since the plasma state can bedetected in real time, upon determining the time point of stabilizationof plasma inside the chamber, consumption of the dummy wafer can besignificantly reduced, and relatively short time can be spent. Forexample, the time point of plasma stabilization can be accuratelydetermined with consumption of a few dummy wafers to dozens of dummywafers.

As can be seen from the graph of FIG. 16, in the plasma process for eachof the dummy wafers, the electron density of the plasma can be detectedin real time using the plasma monitoring system (1000 in FIG. 15)according to the present example embodiment. As such, the electrondensity of the plasma is detected in real time, whereby since the plasmastate inside the chamber can be somewhat predicted, examination of etchrates for a large number of dummy wafers may not be needed. For example,it may be sufficient only to examine etch rates for a few dummy wafers.Here, examination of the dummy wafers may correspond to confirmingaccuracy of the detected electron density of the plasma.

FIG. 17 is a conceptual diagram for explaining utilization of a plasmamonitoring system according to an example embodiment of the inventiveconcept in tool matching between chambers.

Referring to FIG. 17, even though plasma processes are performed in thesame (a), (b), and (c) chambers under the same conditions, states ofplasma inside chambers may be different, as shown in FIG. 17. Forexample, an electron density of plasma Pa of the (a) chamber may be 10,an electron density of plasma Pb of the (b) chamber may be 9, and anelectron density of plasma Pc of the (c) chamber may be 10. Thesedifferences may be caused by, for example, wall conditions of thechambers.

Therefore, the wall conditions of the chambers may be found bymonitoring the electron density of the plasma inside each of thechambers in real time using the plasma monitoring system according tothe present example embodiment, thereby utilizing the plasma monitoringsystem in tool matching for an appropriate plasma process of eachchamber.

FIG. 18 is a graph showing a concept for determining a time point of PMof a chamber using a plasma monitoring system according to an exampleembodiment of the inventive concept.

Referring to FIG. 18, if a plasma process is performed in a chamber fora long period of time, a plasma state inside the chamber deviates froman appropriate plasma state. That is, as shown in FIG. 18, an electrondensity of the plasma starts to exceed an appropriate level after thetime point of PM. Thus, if the time point of PM is reached, PM, such ascleaning and the like, for the chamber should be performed.

The plasma monitoring system according to the present example embodiment(1000 in FIG. 15) monitors the electron density of the plasma inside thechamber in real time, thereby relatively accurately determining the timepoint of PM. Thus, the plasma monitoring system can contribute toimprovement in a plasma process efficiency due to reduction of a PMcycle and maintenance of a good chamber state.

For reference, a symbol Bup on an x axis may refer to the time point ofplasma stabilization, that is, the time point of plasma back-up asdescribed above with reference to FIG. 16, and a symbol S on a y axismay refer to the appropriate electron density of the plasma.

FIG. 19 is a graph depicting electron densities of plasma detected usinga plasma monitoring system according to an example embodiment of theinventive concept in plasma processes for a first wafer and a ninthwafer.

Referring to FIG. 19, a plasma process for one wafer may generallyinclude a plurality of sub-plasma processes. As shown in FIG. 19, eachof the plasma processes for the first wafer (thin line) and the ninthwafer (thick line) may include a plurality of sub-plasma processes. Inaddition, each of the sub-plasma processes may have a correspondingelectron density of plasma, ranges on an x axis, in which the electrondensity is 0; these may be periods of time in which the plasma processis stopped for a short time.

The plasma processes for the first wafer and the ninth wafer may beperformed in the same chamber under the same process conditions. Thus,the plasma electron densities of the sub-plasma processes for the firstwafer and the ninth wafer should be the same. However, as shown in FIG.19, it can be confirmed that the plasma electron densities in thesub-plasma processes are different. Thus, it can be seen that a problemoccurred in the plasma process for the ninth wafer. More precisely, itcan be seen that, among the sub-plasma processes, problems occurred inthe sub-plasma processes (marked by dashed circles) showing noticeabledifferences in plasma electron densities. For reference, since plasmaelectron densities of second to eighth wafers were substantially thesame as the plasma electron density of the first wafer, it can beanticipated that there was not a problem until or after the plasmaprocess for the eighth wafer.

As such, the plasma monitoring system (1000 in FIG. 15) according to thepresent example embodiment measures the electron density of the plasmain the plasma process for each wafer in real time, thereby monitoringproblems during the plasma process, that is, in-process issues in realtime. In addition, when the in-process issues are discovered, causesthereof are analyzed and utilized, whereby the plasma monitoring systemcan contribute to optimization of the plasma process. Here, analysis andutilization of the causes may include, for example, removal of thediscovered causes, solving the problems by changing process conditionswhen the causes cannot be removed, or the like.

FIG. 20 is a flow chart showing a process of monitoring a plasma stateand controlling a plasma process according to an example embodiment ofthe inventive concept. For convenience, descriptions will be made withreference to FIG. 15 together.

Referring to FIG. 20, first, the microwave probe is coupled to theviewport 220 of the chamber 200 (S110). The microwave probe may be themicrowave probe 100 a of FIG. 2A. Of course, instead of the microwaveprobe 100 a of FIG. 2A, the microwave probes 100, 100 b to 100 caccording to the other example embodiments may be coupled to theviewport 220. In addition, when the viewport 220 has the structureillustrated in FIG. 12A, the microwave probe 100 d, 100 e, or 100 f ofFIG. 7A, 7B, or 12B may be coupled to the viewport 220. Coupling themicrowave probe 100 a to the viewport 220 may mean that the networkanalyzer 300 is also coupled to the viewport 220 through the microwaveprobe 100 a. When the microwave probe 100 a is coupled to the chamber200, the computer 800 for analysis may be connected to the networkanalyzer 300, and thereby receive data for a resonant frequencytransferred from the network analyzer 300 in real time. In addition, thecomputer 800 for analysis may not be connected to the network analyzer300 until the network analyzer 300 detects the resonant frequency. Afterthe network analyzer 300 detects the resonant frequency, the computer800 for analysis may be connected to the network analyzer 300, andthereby receive the data for the resonant frequency, which is stored inthe network analyzer 300.

The wafer 500 is arranged on the electrostatic chuck 240 inside thechamber 200 (S120). The wafer 500 may also be arranged on theelectrostatic chuck 240 before the coupling of the microwave probe 100a.

Plasma is generated by injecting the process gases and applying RF powerinto the chamber 200 (S130). The process gases may be injected into thechamber 200 in such a manner that the process gases supplied from thegas supplying sources 600-1, 600-2 are sprayed through the shower head250. The application of the RF power may be performed in such a mannerthat the RF power is respectively applied to the coil 450 on the upperside of the chamber 200 through the upper RF power supply 400-1 and tothe wafer 500 inside the chamber 200 through the lower RF power supply400-2.

In the present operation, the generation of the plasma may refer toperforming a plasma process using the generated plasma. For example, theplasma process may include etching, deposition, diffusion, surfacetreatment, novel material synthesis processes, and the like.

Using the microwave probe 100 a, a microwave is applied into the chamber200, and signals generated inside the chamber 200 are received (S140).An absorption frequency signal of a surface wave, that is, a resonantfrequency signal of the surface wave may be included in the generatedsignals. The microwave may be generated in the network analyzer 300 andapplied into the chamber 200 through the microwave probe 100 a. Inaddition, the signals generated inside the chamber 200 may be receivedthrough the microwave probe 100 a, and transferred to the networkanalyzer 300 through the external wire 310.

A resonant frequency of the surface wave is detected from the receivedsignals, and a plasma state is analyzed based on the resonant frequency(S150). The detection of the resonant frequency may be performed by thenetwork analyzer 300. For example, the network analyzer 300 may detectthe resonant frequency of the surface wave by detecting a peak value ofa reflection coefficient S11.

The analysis of the plasma state may be performed by the computer 800for analysis. For example, the computer 800 for analysis receives thedetected resonant frequency that is input from the network analyzer 300,and calculates an electron density of the plasma using an analysisprogram. The analysis program may be a program for calculating theelectron density of the plasma using Equations (1) to (3), the value ofthe proportional factor k, and the like.

Whether the plasma state is within an allowable range is determined(S160). The determination of whether the plasma state is within theallowable range may be performed by the computer 800 for analysis. Forexample, whether there is a problem in the plasma state may also bedetermined by comparing the calculated plasma electron density with apre-set reference value. Further, when there is a problem in the plasmastate, the computer 800 for analysis may also analyze a cause thereofand suggest new process conditions for the plasma process in question.

If the plasma state is within the allowable range (Yes), monitoring ofthe plasma state is terminated. If the plasma state is outside of theallowable range (No), process parameters of the plasma process areadjusted (S170). The adjustment of the process parameters may beperformed through, for example, increase or decrease in pressures of theprocess gases, increase or decrease in applied RF power, or the like.The adjustment of the process parameters may be performed based on dataobtained through a simulation in the computer 800 for analysis.

After the adjustment of the process parameters, the process returns toarranging a new wafer inside the chamber (S120), and the plasma processand monitoring thereof are performed again.

Since the method of monitoring the plasma state according to the presentexample embodiment is performed using the microwave probe, which isnon-invasively coupled to the chamber 200 and has the structureillustrated in any one of FIG. 1A to FIG. 12B, the plasma state insidethe chamber 200 can be precisely detected and monitored by the methoddue to a high reception sensitivity to the signals inside the chamber200, with no influence on the plasma state inside the chamber 200. Inaddition, the method of controlling the plasma process according to thepresent example embodiment appropriately controls process conditions ofthe plasma process based on accurate monitoring of the plasma stateinside the chamber 200 using the microwave probe, thereby optimizing theplasma process.

FIG. 21 is a flow chart showing a process of fabricating a semiconductordevice through the control of the plasma process according to an exampleembodiment of the inventive concept. In the interest of brevity, detailswhich have been described above with reference to FIG. 20 may be onlybriefly described or omitted.

Referring to FIG. 21, first, the methods of monitoring the plasma stateand controlling the plasma process described above with reference toFIG. 20 are performed. The methods of monitoring the plasma state andcontrolling the plasma process may include a plasma process for thewafer 500. For example, the generating of the plasma (S130) as describedwith reference to FIG. 20 may correspond to the plasma process for thewafer 500.

For reference, in FIG. 21, operation “S160” may refer to performing themethods of monitoring the plasma state and controlling the plasmaprocess as described with reference to FIG. 20, and an arrow fromoperation “S160” may mean that the process proceeds to the nextoperation since the methods of monitoring the plasma state andcontrolling the plasma process are completed. More precisely, inoperation S160 of determining the allowable range of the plasma state inFIG. 20, the arrow from operation “S160” may mean that since the plasmastate is within the allowable range (Yes), the methods of monitoring theplasma state and controlling the plasma process are completed, and theprocess proceeds to the next operation.

A subsequent semiconductor process for the wafer 500 is performed(S210). The subsequent semiconductor process for the wafer 500 mayinclude various processes. For example, the subsequent semiconductorprocess for the wafer 500 may include a deposition process, an etchingprocess, an ion process, a cleaning process, and the like. Thedeposition process, the etching process, the ion process, the cleaningprocess, and the like may be processes using plasma, or may be processesnot using plasma. If the processes set forth above are processes usingplasma, the methods of monitoring the plasma state and controlling theplasma process described above may be used again. The subsequentsemiconductor process for the wafer 500 is performed, thereby formingintegrated circuits and wires required for a semiconductor device inquestion. The subsequent semiconductor process for the wafer may alsoinclude a process of testing a wafer-level semiconductor device.

The wafer 500 is separated into individual semiconductor chips (S220).The separation into the individual semiconductor chips may be performedthrough a sawing process using a blade or laser.

Next, a packaging process for the semiconductor chips is performed(S230). The packaging process may refer to mounting the semiconductorchips on a PCB and sealing the chips with a sealant. The packagingprocess may include forming a stack package by stacking a plurality ofsemiconductors as multiple layers on the PCB, or forming a package onpackage (POP) structure by stacking a stack package on another stackpackage. A semiconductor device or a semiconductor package may becompleted through the packaging process for the semiconductor chips.After the packaging process, a test process for the semiconductorpackage may be performed.

The method of fabricating a semiconductor device according to thepresent example embodiment performs plasma state monitoring and plasmaprocess control using the plasma monitoring system 1000 of FIG. 15,thereby optimizing the plasma process. In addition, the method offabricating a semiconductor device fabricates semiconductor devicesbased on the optimized plasma process, thereby realizing excellent andhighly reliable semiconductor devices.

While the inventive concept has been particularly shown and describedwith reference to example embodiments thereof, it will be understoodthat various changes in form and details may be made therein withoutdeparting from the spirit and scope of the following claims.

1. A method of fabricating a semiconductor device, the methodcomprising: non-invasively coupling a microwave probe to a viewport of achamber for a plasma process; arranging a wafer inside the chamber;generating plasma by injecting a process gas into the chamber andapplying RF power to the chamber; applying a microwave into the chamberthrough the microwave probe, and receiving signals generated inside thechamber through the microwave probe; and detecting a resonant frequencyamong the received signals, and analyzing a plasma state inside thechamber based on the resonant frequency, wherein the microwave probecomprises a body and a head at a first end of the body, and the applyingof the microwave and the receiving of the signals are performed throughthe head which contacts an outer surface of the viewport during thenon-invasively coupling the microwave probe to the viewport.
 2. Themethod according to claim 1, wherein the microwave probe comprises aground cover surrounding the body and the head, the ground covercomprising a through-hole in a central portion of a base of the groundcover, and in the non-invasively coupling of the microwave probe, anouter rim of the ground cover that extends away from the base is coupledto a wall of the chamber to be grounded, and the body extends to theoutside of the ground cover through the through-hole to be electricallyconnected to a network analyzer through a connector that is at a second,opposite end of the body.
 3. The method according to claim 1, wherein inthe analyzing of the plasma state, an electron density of the plasma iscalculated based on the resonant frequency.
 4. The method according toclaim 3, further comprising: comparing the electron density of theplasma with a pre-set electron density value; and adjusting processparameters for generating plasma if the calculated electron density ofthe plasma is outside of an allowable range around the pre-set electrondensity value.
 5. The method according to claim 3, further comprising:comparing the electron density of the plasma in the plasma process forthe wafer with an electron density of plasma in the plasma process foranother wafer arranged inside the chamber; determining if there is adifference between the electron densities; if it is determined thatthere is a difference between the electronic densities, analyzing acause of the difference; and controlling the plasma process based on theanalysis.
 6. The method according to claim 3, wherein the wafer is adummy wafer which is not subjected to an actual plasma process, andwherein the method comprises determining a time point of stabilizationof the plasma inside the chamber based on the electron density of theplasma.
 7. The method according to claim 3, further comprisingdetermining a time point of preventive maintenance (PM) based on theelectron density of the plasma.
 8. The method according to claim 1,wherein the plasma process comprises any one of etching, deposition, anddiffusion processes for the wafer, and in the generating of the plasma,the wafer is subjected to any one of etching, deposition, and diffusionprocesses.
 9. The method according to claim 1, wherein if the plasmastate is within an allowable range in the analyzing of the plasma state,the method comprises: performing a subsequent semiconductor process forthe wafer; separating the wafer into individual semiconductor chips; andpackaging the semiconductor chips.
 10. A method of fabricating asemiconductor device, the method comprising: generating plasma byinjecting a process gas into a chamber, in which a wafer is arranged,and by applying RF power to the chamber; applying a microwave into thechamber and receiving signals generated inside the chamber, through amicrowave probe non-invasively coupled to a viewport of the chamber, themicrowave probe comprising a body and a head at one end of the body; anddetecting a resonant frequency among the received signals, and analyzinga plasma state inside the chamber based on the resonant frequency. 11.The method according to claim 10, wherein the head comprises a flatplate, and before the generating of the plasma, the microwave probe isnon-invasively coupled to the viewport of the chamber such that asurface of the head contacts an outer surface of the viewport.
 12. Themethod according to claim 10, wherein the microwave probe comprises aground cover surrounding the body and the head, the ground covercomprising a base having a through-hole in a central portion thereof,and before the generating of the plasma, the microwave probe isnon-invasively coupled to the viewport of the chamber such that an outerrim of the ground cover that extends away from the base is coupled to awall of the chamber to be grounded.
 13. The method according to claim10, wherein in the analyzing of the plasma state, a network analyzerconnected to the microwave probe detects the resonant frequency, and acomputer calculates an electron density of the plasma based on theresonant frequency.
 14. The method according to claim 13, furthercomprising: comparing the electron density of the plasma with a pre-setelectron density value; and adjusting process parameters for asubsequent generating plasma step if the electron density of the plasmais outside of an allowable range around the pre-set electron densityvalue.
 15. The method according to claim 10, wherein the plasma processcomprises any one of etching, deposition, and diffusion processes forthe wafer, and in the generating of the plasma, the wafer is subjectedto any one of etching, deposition, and diffusion processes.
 16. Themethod according to claim 10, wherein if the plasma state is within anallowable range in the analyzing of the plasma state, the methodcomprises: performing a subsequent semiconductor process for the wafer;separating the wafer into individual semiconductor chips; and packagingthe semiconductor chips.
 17. A method of fabricating a semiconductordevice, the method comprising: non-invasively coupling a microwave probeto a viewport held in an outer wall of a chamber for a plasma process;generating plasma by injecting a process gas into the chamber andapplying RF power to the chamber; applying a microwave into the chamberthrough the microwave probe; receiving signals generated inside thechamber through the microwave probe; detecting a resonant frequencyamong the received signals; and analyzing a plasma state inside thechamber based on the resonant frequency including determining anelectron density of the plasma based on the resonant frequency; whereinthe microwave probe comprises a body and a head at a first end of thebody, and the applying of the microwave and the receiving of the signalsare performed through the head which contacts an outer surface of theviewport during the non-invasively coupling the microwave probe to theviewport.
 18. The method according to claim 17, wherein the microwaveprobe further comprises a ground cover comprising a base having athrough-hole defined therein through which the body extends and an outersidewall extending outwardly away from an outer periphery of the base,and wherein the outer sidewall contacts an outer wall of the chamberduring the non-invasively coupling the microwave probe to the viewport.19. The method according to claim 18, wherein the microwave probefurther comprises a filter coupled to the outer sidewall and surroundingthe head, wherein the viewport comprises a central portion and an outerportion surrounding the central portion, and wherein the head contactsat least a portion of the central portion of the viewport and the filtercovers at least a portion of the outer portion of the viewport duringthe non-invasively coupling the microwave probe to the viewport.
 20. Themethod according to claim 18, wherein the viewport comprises a channeldefined therein, and wherein the body and the head are received in thechannel with the head contacting an end of the channel during thenon-invasively coupling the microwave probe to the viewport. 21.-36.(canceled)